Tea is the most popular flavored and functional drink worldwide. The nutritional value of tea is mostly from the tea polyphenols that are reported to possess a broad spectrum of biological activities, including anti-oxidant properties, reduction of various cancers, inhibition of inflammation, and protective effects against diabetes, hyperlipidemia and obesity. Tea polyphenols include catechins and gallic acid in green and white teas, and theaflavins and thearubigins as well as other catechin polymers in black and oolong teas. Accurate analysis of black tea polyphenols plays a significant role in the identification of black tea contents, quality control of commercial tea beverages and extracts, differentiation of various contents of theaflavins and catechins and correlations of black tea identity and quality with biological activity, and most importantly, the establishment of the relationship between quantitative tea polyphenol content and its efficacy in animal or human studies. Global research in tea polyphenols has generated much in vitro and in vivo data rationally correlating tea polyphenols with their preventive and therapeutic properties in human diseases such as cancer, and metabolic and cardiovascular diseases etc. Based on these scientific findings, numerous tea products have been developed including flavored tea drinks, tea-based functional drinks, tea extracts and concentrates, and dietary supplements and food ingredients, demonstrating the broad applications of tea and its extracts, particularly in the field of functional food.

Gardenia jasminoides, grown in multiple regions in China, was commonly used as a natural yellow dye but has been one of the popular traditional Chinese medicines since the discovery of its biological property a few decades ago. It has been reported that G. jasminoides possess multiple biological activities, such as antioxidant properties, hypoglycemic effect, inhibition of inflammation, antidepression activity, and improved sleeping quality. In this review, our aim was to have a comprehensive summary of its phytochemistry including the extraction, isolation, and characterization of volatiles and bioactive molecules in G. jasminoides, focusing on the two major phytochemicals, genipin and crocin, which possess potent medicinal properties. Furthermore, this study attempted to establish a structure-activity relationship between the two major series of molecules with two pharmcophores and their biological activities, which would serve further exploration of the properties of phytocompounds in G. jasminoides as potential functional foods and medicines.